1. Field of the Invention
This invention relates to the sealing of surface cracks in metals and especially to a method for sealing surface cracks in metals by the use of a scanning, high-energy beam.
2. Description of the Prior Art
High-energy beams have been used for a number of years to apply surface treatments to many materials. A beam, such as a laser or electron beam, has been employed to melt the surface layer of materials to improve their mechanical properties. It was thought that a beam could be used to fuse the surface of cracks in metals and thereby seal the crack to the environment. Once the surface of a crack is sealed, the interior can be healed by hot isostatic pressing. The difficulty in using a high-energy beam to seal surface cracks is that surface cracks tend to become larger because application of a high-energy beam induces thermal shock in the material. The large thermal shock associated with a high-energy beam generates thermal strain in the surface which prevents the healing of the crack.